Islam Ashna, Sultana Mahfuza Sharifa, Begum Aleya, Yeasmin Selina
Department of Environmental Sciences, Jahangirnagar University, Savar, Dhaka 1342, Bangladesh.
Radiat Prot Dosimetry. 2013 Dec;157(2):255-64. doi: 10.1093/rpd/nct135. Epub 2013 May 27.
A small part of the palaeo beach formation extending along the south-eastern fringe of Bangladesh was selected as study area. The sandy beach formation, enriched with heavy mineral sands containing ²³²Th-bearing monazite, is covered by a thin layer of top soil. Activity concentrations of natural and artificial radionuclides (²³⁸U, ²²⁶Ra, ²³²Th, ⁴⁰K and ¹³⁷Cs), outdoor and indoor annual effective dose rates and the radiation hazard indices were determined in the soil. The radionuclides, investigated by direct gamma-ray spectrometry using HPGe detector, showed that mean activity concentrations of ²²⁶Ra, ²³⁸U, ²³²Th, ⁴⁰K and ¹³⁷Cs in soils were 254.53 ± 6.66, 193.95 ± 7.23, 362.18 ± 6.45, 135.79 ± 24.63 and 2.21 ± 0.49 Bq kg⁻¹ respectively. The mean value of radium equivalent activity, external and internal hazards, outdoor absorbed dose rate and total annual effective dose rate were 783.24 Bq Kg⁻¹, 2.12 and 2.80, 354.32 nGyh⁻¹ and 2.52 mSv y⁻¹, respectively, which exceed the average worldwide limit and may pose a radiological threat to inhabitants.
沿着孟加拉国东南边缘延伸的古海滩地层的一小部分被选为研究区域。富含重矿物砂（含含钍-232独居石）的沙滩地层被一层薄薄的表土覆盖。测定了土壤中天然和人工放射性核素（钍-238、镭-226、钍-232、钾-40和铯-137）的活度浓度、室外和室内年有效剂量率以及辐射危害指数。使用高纯锗探测器通过直接伽马射线能谱法研究的放射性核素表明，土壤中镭-226、钍-238、钍-232、钾-40和铯-137的平均活度浓度分别为254.53±6.66、193.95±7.23、362.18±6.45、135.79±24.63和2.21±0.49 Bq kg⁻¹。镭当量活度、外照射和内照射危害、室外吸收剂量率和年总有效剂量率的平均值分别为783.24 Bq Kg⁻¹、2.12和2.80、354.32 nGyh⁻¹和2.52 mSv y⁻¹，均超过全球平均限值，可能对居民构成辐射威胁。
